Lubricant compositions



LUBRICANT COMPOSITIONS Oliver L. Harle, Berkeley, and John R. Thomas, Albany, (ialif assignors to California Research Corporation,

sen Francisco, Calif a corporation of Delaware No Drawing. Application June 29, 1954, Serial No. 440,263

12 Claims. 01. 252-491 This invention relates to novel lubricant compositions. More particularly, the invention is concerned'with novel lubricating oil compositions having improved oxidation and .corrosion inhibiting properties.

Lubricating oils generally have a tendency to deteriorate due to oxidation and form decomposition products which are corrosive to metals. Since lubricating oils in use today almost invariably come into contact with metal surfaces, the problem of overcoming oxidation and corrosion is considered to be one of major importance. Operating conditions encountered in modern internal combustion engines in which these oils are commonly employed involve" increased temperatures, higher speeds and reduced clearances which tend to promote decomposition and the formation of corrosive products. Furthermore, these engines generally employ alloy metal bearings which, besides their possible catalytic effect on the decomposition of the hydrocarbon type mineral lubricating oils, are easily corroded and this, in turn, has seriously accentuated the oxidation and corrosion problems in mineral lubricating oils.

Inhibitors have been added to lubricating oils to improve their resistance 'to decomposition and avoid corrosivity. Mineral lubricating oils for internal combustion engines, due to the severity of their service, have also been compounded with additional agents such as wear inhibitors,

sludge inhibitors and detergents to loosen and suspend products of decomposition and counteract their eflect. Unfortunately, many of these agents may adversely affect the efiiciency of the oxidation and corrosion inhibitors and it is a problem to find inhibitors which will function in combination with them. Furthermore, some of the most efiective oxidation and corrosion inhibitors contain active sulfur and are, therefore, extremely corrosive to silver and similar metals which are subject to attack by active sulfur. These types of metals, although once not so widely used in contact with lubricating oils and therefore considered to constitute only a minor problem, are being increasingly employed today. Particularly in certain important classes of internal combustion engines as, for example, marine and railroad diesel engines, silver metal-containing bearings are more and more common and the problem of providing proper lubrication for them is one of major importance.

It is, therefore, a general object of this invention to provide lubricating oil compositions having improved antioxidant and anticorrosion properties.

A more particular object of the invention is .to provide lubricating oil compositions which are noncorrosive to silver and similar metals.

Another more particular object is the provisiou of Patented June 11, 1957 HQQ 2 mineral lubricating oil compositions in which the tendency to corrode alloy bearings of internal combustion engines has been inhibited.

A further and somewhat related object is to provide compounded mineral lubricating oil compositions having improved anticorrosion properties without adversely affecting the stabilizing, deterging and lubricating qualities of the hydrocarbon oil composition.

Another and still more particular object of the invention is the provision of mineral lubricating oil compositions which are noncorrosive to silver metal-containing bearings of the type employed in railroad diesel engines.

Additional objects of the invention will become apparent from the description and claims which follow.

In the accomplishment of the above objects, it has been found that compositions comprising an oil of lubricating viscosity and a complex of an acid of the group consisting of arsenic acid, arsenious acid, antimonic acid and antimonious acid with a member of the group consisting of glycols and polyhydroxy benzenes have greatly enhanced anticorrosion properties. it has also been found that, in particular, compositions comprising a compounded mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and such a complex are substantially noncorrosive.

The normal tendency of oils to become oxidized and corrosive is definitely inhibited in the improved compositions of the invention. Metal surfaces in general are not corroded by contact with these compositions and internal combustion engine alloy bearings, in particular, are remarkably benefited. Bearings of silver and similar metals which, as stated above are increasingly important due to their presently expanded use in marine and railroad diesel engines, are not corroded by these compositions whereas conventional oxidation inhibited oils have severely pitted and corroded such bearings. The advantages of 'these improvements are obtained in the compositions of this invention without loss of stability or detergency in the composition.

The complexes of arsenic, arsenious, antimonic and antimonious acids are not only very eifective alone in the oils as primary inhibitors of oxidation but also function in combination with other antioxidants as auxiliary inhibitors. They are, in addition, remarkably effective as metal deactivators for the common bearing metals, such as copper and lead, which normally tend to accelerate the decomposition of lubricating oil compositions.

The acid complexes of the compositions according to this invention are prepared by the reaction of a mixture of the acid and glycol or polyhydroxy benzene. The mixtures are ordinarily heated to accelerate the reaction. Although the nature of the reaction is not definitely known, it is believed that two of the hydroxyl groups of'a single glycol or polyhydroxy benzene react with the acid to form what is commonly termed a metal chelate compound. These compounds are characterized by a claw type of structure in which one or more rings of similar or unlike structure due to the use of mixed glycols or polyhydroxy benzenes are formed including the arsenic or antimony.

The glycols which are reacted with the arsenic, arsenious, antimonic or antimonious acids are preferably. alphaand beta-alkanediols containing from 2 to 18 carbon atoms. Such glycols include, for example ethylene' g y l. and 3-p p i 1, rw a s iql.

hydroxy benzene.

butanediol, 2,4-pentanediol, 1,2-hexanediol, 2-methyl-1,3- pentanediol, 1,2- and 1,3-octylene glycols including 2- ethylhexaue-LB-dioi, 1,2-dodecanediol, 2,4-diethyl-octane- 1,3-diol, and 2,4,6-triethyl-decane-1,3-diol. The glycols containing from 6 to 10 carbon atoms are more preferred since they impart an optimumdegree of oil solubility to the complexes. Alphaand beta-octylene glycols such as 2-ethylhexane-1,3-diol have been found to be the most satisfactory for present purposes since they give unusually velfective oxidation and corrosion inhibitors.

The polyhydroxy benzenes are preferably vicinal dihydric phenols such as catechol, 3,4-dihydroxy toluene, tert.- butylcatechol, cetylcatechol, and the like. They may contain additional hydroxyl groups as, for example, 1,2,4-tri- Alkyl catechols containing from 2 to 18 carbon atoms in the alkyl group are at present most preferred since the arsenates, arsenites, antimonates and antimonites prepared from them possess the most satisfactory oil solubility characteristics.

plexes for the lubricating oil compositions of this invention, other acid compounds may also be employed. Such compounds include ortho-arsenic acid, HsAsO-yl/ZI-IzO; meta-arsenic acid, HAsOa; pyro-arsenic acid, HrAszOq; arsenic pentachloride, AsCls; arsenic oxide, AszOs; arsenates such as ammonium arsenate; arsenious acid, HsASOs or HAsOz; arsenious acid anhydride or arsenious oxide, AszOs; arsenious chloride, AsCls; arsenious triiodide, ASI3; arsenites such as ammonium arsenite; ortho-antimonic acid, HsSbO-r; meta-antimonic acid HSbOs; pyroantimoni-c acid, H4Sb207; antimonic chloride, SbCl5; antimonic acid anhydride or antimonic oxide, SbzOs; antimonates such as ammonium antimonate; ortho-antimonious acid, H3SbOs; meta-antimonious acid, HSbOz; pyroantimonius acid, H4Sb205; antimonious chloride, SbCl3; antimonious acid anhydride or antimonious oxide, SbzOs; and antimonites such as ammonium antimonite.

The complex of the arsenic, arsenious, antimonic and antimonious acids with glycol or polyhydroxy benzene is present in the compositions of the invention in an amount at least sufficient to inhibit corrosion or oxidation. Small amounts, usually from about 0.01 to about 5.0 percent by weight based on the oil, are effective. Proportions ranging from about 0.05 to about 1.0 percent are preferred in most lubricating oil compositions. Concentrates containing larger proportions, up to 50 percent, either in solution or suspension, are particularly suitable in compounding operations.

Any of the well known types of oils of lubricating viscosity are suitable base oils for the compositions of the invention. They include hydrocarbon or mineral lubricating oils of naphthenic, paraflinic, and mixed naphthenic and parafl'inic types. They may berefined by any of the conventional methods such as solvent refining and acid refining. Synthetic hydrocarbon oils of the alkylene polymer type or those derived from coal and shale may also be employed. Alkylene oxide polymers and their derivatives'such as the propylene oxide polymers and their ethyl esters and acetyl derivatives in which the terminal hydroxyl groups have been modified are also suitable. Synthetic oils of the dicarboxylic acid ester type including dibutyl adipate, di-2-ethylhexyl sebacate, di-u- :rexyl fumaric polymer, di-lauryl acylate, and the like may be used. Alkyl benzene types of synthetic oils such 18 tetradecyl benzene, etc. are. also included. Liquid esters of acids of phosphorus including tricresyl phosphate, .diethyl esters of decane phosphonic acid, and the like may also be employed. Also suitable are the polysiloxane oils of the type of polyalkyl-, polyaryl-, polyalkoxyand polyaryloxy siloxanes such as polymethyl siloxane, polymethylphenyl siloxane and polymethoxyphenoxy siloxane and silicate ester oils such as tetraalkyland tetraaryl silicates of the tetra-Z-ethylhexyl silicate and tetra-p-tert.-butylphenyl silicate types.

In a preferred embodiment of the invention, as mentioned above, the complexes of a particular acid with glycol or polyhydroxy benzene are employed in combination with compounded mineral lubricating oils of the internal combustion engine type which are normally corrosive to alloy bearings. In such an embodiment, as in the case of the other straight oils of lubricating viscosity, a major proportion of the lubricating oil normally corrosive to metals and/or subject to oxidation and a small amount, sufficient to inhibit said corrosion and/ or oxidation, of the acid complex provides a remarkably improved composition. These compounded oils customarily contain detergents such as the oil-soluble petroleum sulfonates and stabilizers such as the metal alkyl phenates. Other agents shch' as oiliness agents, viscosity index improvcrs, pour point depressants, blooming agents, peptizing agents, etc. may also be present.

In further illustration of the invention, the following examples are submitted showing the preparation of the acid complexes and evaluation of their effectiveness as corrosion inhibitors and antioxidants in oil composition. Unless otherwise specified the proportions given in these examples are on a weight basis.

EXAMPLE 1 Into a glass reaction flask equipped with a reflux condenser and a continuous water separation trap is placed 0.25 mole of arsenious oxide in a solution of 1.0 mole of 2-ethylhexanediol-1,3 in 200 grams of toluene; The

mixture is then refluxed and the Water resulting from the esterification reaction is collected until no further water is evolved. The yield of water is 0.75 mole which is consistent with complete esterification of the arsenious oxide. a

The toluene is removed from the liquid reaction product by distillation at reduced pressure. The di(2-ethyl hexanediol-1,3) arsenite remains as a pale yellow fluid which is insoluble in Water but "soluble in mineral oil.

EXAMPLE 2 fluid soluble in mineral oil but substantially insoluble in' water.

EXAMPLE 3 0.5 mole of arsenious oxide is added to a solution of 1.0 mole of butanediol-2,3 in 200 grams of toluene. The mixture is refluxed in a glass reaction vessel fitted with a reflux condenser and continuou water separation trap until water is no longer evolved. About 0.5 mole of water is collected which corresponds to one-half esterification of the arsenious oxide.

The liquid reaction mixture is distilled to remove the toluene. The mono(butanediol-2,3) arsenite remains as a pale yellow fluid.

EXAMPLE 4 To a solution of 1.0 mole 2-ethylhexanediol-1,3 in 200 grams of toluene is added 0.25 mole of arsenic oxide. The mixture is refluxed under a condenser fitted with a continuous water separation trap and the water resulting from the esterification reaction is collected. The yield of water is found to be 0.75 mole which is consistent with complete esteriiication of the arsenic oxide. I

The liquid reaction product is distilled at reduced pressure to remove the toluene. The di(2-ethylhexanediol- 1,3) arsenate remains as a pale yellow fluid soluble in mineral oil and insoluble in water.

EXAMPLE 5 To a solution of 2 moles of 4-tert.-butylcatechol in 400 grams of toluene is added 1 mole of arsenious oxide. The mixture is refluxed in a glass reaction vessel equipped with a reflux condenser and continuou water separation trap until water is no longer evolved. Approximately 1 mole of water is collected.

The liquid reaction mixture is distilled under reduced pressure to remove the toluene solvent. The mono(4- tert.-butylcatechol) arsenate product which remains is a light yellow crystalline solid. It is not readily soluble in water but is substantially soluble in mineral oil.

EXAMPLE 6 0.5 mole of arsenic oxide is added to a solution of 2.0 moles of 4-tert.-butylcatechol in 400 grams of toluene in a glass reaction flask. The flask is equipped with a reflux condenser and a trap for continuous water separation. The contents of the flask are refluxed and the water formed in the reaction of the 4-tert.-butylcatechol and the arsenic oxide collected until no further water is evolved. The water collected corresponds to the theoretical of about 1.5 moles for complete esterification.

The toluene solvent is distilled from the liquid reaction mixture under a vacuum. The product consisting of di(4-tert.-butylcatechol) arsenate is a light yellow solid material soluble in mineral oil but substantially insoluble in water.

EXAMPLE 7 To a solution of 1.0 mole 2-ethylhexanediol-1,3 in 200 grams of toluene is added 0.5 mole of arsenic oxide. The mixture is refluxed in a glass reaction flask equipped with a reflux condenser and continuous water separation trap until the reaction is complete as indicated'by water no longer being evolved. About 0.5 mole of water is collected which corresponds to the theoretical for one-half esterification of the arsenic oxide.

The toluene solvent is stripped from the liquid reaction mixture by distillation under reduced pressure. The mono(2-ethylhexanediol-l,3) arsenate which remains is a pale yellow liquid. It is insoluble in water and readily soluble in mineral oil.

EXAMPLE 8 Into a solution of 2.0 moles of pentaerythritol monooleate and 400 grams of toluene is placedL'O mole of arsenious oxide. The mixture is refluxed under a condenser fitted with a continuous water separation trap until the formation of water is complete. About 1.0 mole of water is collected which corresponds to the theoretical for one-half esterification of the arsenious oxide.

The liquid reaction mixture is distilled at reduced pressure to remove the toluene solvent. The mono(pentaerythritol monooleate) arsenite thus obtained is a pale yellow fluid. It is readily soluble in mineral oil but insoluble in water.

EXAMPLE 9 To a mixture of 22.8 grams (0.10 mole) ofantimony trichloride (antimonious chloride) is added a solution of 33.2 grams (0.20 mole) of 4-tert.-butylcatechol 100 milliliters of methanol. The mixture is stirred vigorously as 50 milliliters of concentrated ammonium hydroxide (about 28% ammonia) are added. After heatingthe mixture about one-half hour on a steam plate, 150' milliliters of water are added. The mixture is then cooled.

A precipitate is formed which is removed by filtration, washed with water and dried in a vacuum oven at C. The di(4-tert.-butylcatechol) antimonite thus obtained is a white solid material which is moderately soluble in mineral oil but nearly insoluble in water.

EXAMPLE 10 T o a solution of 29.9 grams (0.10 mole) of antimony pentachloride (antimonic chloride) in milliliters of methanol are added 49.8 grams (0.30 mole) of 4-tert. butylcatechol dissolved in 100 milliliters of methanol. About 50 milliliters of concentrated ammonium hydroxide (approximately 28% ammonia) are then added to the green-colored solution and the mixture is concentrated to approximately 100 milliliters on a steam plate.

About 400 milliliters of water are added to the reaction mixture. A tarry product is separated and washed with more water. The product is then dissolved in 200 milliliters of toluene to provide a concentrate of tri(4- tert.-butylcatechol) antimonate which is miscible in mineral oil.

Although the complexes of arsenic and antimony with glycol or polyhydroxy benzene are distinctly superior and provide the preferred lubricating oil compositions of the invention, various amine salts and esters of the acid complexes may also be employed. The amine salts may be prepared by heating a mixture of the complex of arsenic acid, arsenious acid, antimonic acid or antimonious acid with glycol or polyhydroxy benzene and an organic amine such as trimethyl amine, triethanol amine, lauryl amine, phenyl-alpha-naphthylamine, metaxylylene diamine, amino phenol, pyridine, morpholine, etc. The esters may be prepared by heating the acid complex of arsenic or antimony with aliphatic alcohols and'glycols such as ethyl alcohol, butyl alcohol, 2-ethylhexanediol-l,3, pcntaerythritol, cetyl alcohol, etc.

The effectiveness of the lubricating oil compositions of the invention containing the complexes of arsenic and antimony is demonstrated by the copper-lead strip corrosion test. In this test a polished copper-lead strip is weighed and immersed in 300 cubic centimeters of test oil in a 400-milliliter lipless Berzelius beaker. The test oil is maintained at 340 F. under a pressure of one atmosphere of air and stirred with a mechanical stirrer at 1,000 R. P. M. After two hours a synthetic naphthenate catalyst is added to provide the following catalytic metals:

Percent by weight The test is continued 20 hours. The copper-lead strip is then removed, rubbed vigorously with a soft cloth and weighed to determine the net weight loss.

The test oils in this instance include both a mineral lubricating oil which is an acid refined medicinal type white mineral oil and a compounded mineral lubricating oil of the internal combustion engine type which is normally corrosive to alloy bearings. In this case the compounded oil consists of a solvent refined SAE 40 mineral lubricating oil base having a viscosity index of 60 and containing 10 millimoles per kilogram of neutral calcium petroleum sulfonate and 20 millimoles per kilogram of calcium alkyl phenate, sulfurized. The results of the test are shown in the following table. The concentrations of the acid complex employed are given ineither percent by weight or in millimoles of arsenic or antimony per kilogram of oil. l

Table I COPPER-LEAD STRIP CORROSION TEST Copper- Lead Additive Base oil Strip Weight Loss (mes) None Mineral lub. oil 60. 4 20 mhJkg. di(2-ethy1hexanediol-l,3) ar- Same 14.3

sen e. 20 mM;/kg. di(4-tert.-butylcatechol) 21- Same 25.0

senate. 1' 20 mM./kg. mono(4-tcrt.-butylcatecl1ol) Same 29.4

antimonite. None Oompounded 01L 257. 9 0. di(2-ethylhexanedl0l-1,3) arsenite.- Same 7.1 0.6% mono(2-methylpentanediol-2,4) ar- 6. 8

seal e. 0.6% mixed mono and di(butanedio1-2,3) 9. 1

arsemtes. 0.5% di(2-ethylhexanediol-1,3) arsenate. 26. 1 0.5% mono(4-tert.-butylcatechol) arse- 29.2

n to. 0.5% di(4-tert.-butylcatechol) arsenateu- Same 56.0 0.5% mono(2-ethylhexanediol-L3) arse- Same 15.6

nate. 40 mMJkg di(4-tert.-butylcatechol) 29.4

antirnonite. 5 mMJkg. tri(4-tert.-butylcatechol) an- 77.1

timonate. 40 rnM./kg. (li(2ethylheXanedi0l-1,3) 18.7

' antimonite.

As shown by the above test data, straight mineral lubrieating oil alone gives a copper-lead strip weight loss due to corrosion of over 60 milligrams in the 20-hour period. By way of distinction, compositions of the invention containing the same straight mineral lubricating oil as a ase plus arsensic and antimony complexes as corrosion inhibitors give as little as 14.3 milligrams weight loss. In the case of the conventional compounded mineral lubricating oil of the internal combustion engine type which is normally corrosive, the improvement is even more remarkable. The compounded oil alone gives a copper-lead strip weight loss due to corrosion of almost 258 milligrams in the 20-hour period whereas the lubricating oil compositions of the invention containing the same compounded base oil plus a complex of arsenic or antimony with a glycol or polyhydroxy benzene result in very little corrosion loss, one being as low as 6.8 milligrams.

, The performance characteristics of the lubricating oil compositions of the invention are also illustrated by their evaluation in a number of engine tests. The engine procedures and techniques, though conventional and well known in the lubricating oil art, are briefly described for the sake of convenience in the following paragraphs along with the test data.

In the L4 engine test the corrosion characteristics of the oils are determined in a Chevrolet standard 6-cylinder engine in a typical laboratory installation. Weighed copper-lead test bearings and new piston rings are installed. The test is run at a constant engine speed at about 3,000 R. P. M. under a load of 30 brake horsepower for a total of 36 hours subsequent to a run-in period of 8 hours. The outlet temperature of the jacket :oolant is 200 F. and the oil sump temperature is 280 F. At the conclusion of the test the engine is disassembled 1nd inspected for varnish and sludge deposits and the larious parts are rated on a cleanliness scale of 0 to 10 vith 10 being the best. The bearings are. Weighed to letermine the weight loss per whole bearing due to :orrosion. The reference oil is a solvent refined SAE 30 nineral lubricating oil base with 7 mM./kg. of neutral cal- :ium petroleum sulfonate and 16 mM./kg. of calcium Elkyl 'phenate, sulfurized. Illustrative test results are given in the following table.

, percent sulfur fuel.

Table I Weight Loss, mgJWhole Bearing Oil Gompounded oil (reference oil) more than 900. 0.5% mixed mono and di(2-methy1pentanediol-2,4) 452.

arsenite. 7

" vention effective in reducing the bearing corrosion loss from more than 900 milligrams to less than 500 milligrams per bearing even at the low concentration of corrosion inhibitor employed, but it also gives a very high performance rating so far as engine deposits and cleanliness are concerned.

In the L-l engine test the detergoncy and wear inhibiting characteristics of the lubricating oil compositions of the invention are evaluated in a single cylinder caterpillar diesel test engine. The piston rings, cylinder liner, valves, etc. are standard production units of the diesel type. The engine is operated at a speed of 1,000 R. P. M under a load of approximately 20 brake horse-power. The oil temperature to the bearings is to F. After 120 hours operations with 0.4 percent sulfur-containing fuel, the engine is inspected for cleanliness. The reference oil is the same as described above. Illustrative test data are set out in the following table.

Table .111

Oil Engine Condition Oompounded oil (reference 011) Clean.

The above test data show that the lubricating oil compositions of the invention are excellent diesel engine lubricating oils of the heavy duty type.

The L-l and L-4 engine tests referred to above are more fully described in the C. R. C. Handbook, 1946 edition, Coordinating Research Council, New York New York.

In the Navy propulsion load test described in MIL.

l7269'(Ships) 17 July 1952, the compositions of the invention are evaluated as diesel engine lubricating oils under severe operating conditions. The tests are run in a General Motors 4-cylinder diesel engine using one Copper-lead bearings are employed. The tests are run at a constant speed of 1,800 R. P. M. under a load of 30 brake horse-power per cylinder. The crankcase temperature is 250 F. The present test is run continuously to simulate railroad diesel engine performance unlike the standard Navy test procedure which permits regular 4-hour shutdown periods. Sea water was also excluded for the same reason. The reference .oil is the same as described above; Test results areas follows:

Table IV Weight Loss, rugs/Whole Bear- In the Navy engine tests shown above, the bearing weight loss due to corrosion by the reference oil, a conventional heavy duty compounded oil, is extremely high. Such an oil would be impossible to use for any prolonged period of time without shutdown. By way of distinction, the lubricating oil composition of the invention containing arenic or antimony complexes gives remarkably low corrosion losses after as much as 200 hours of continuous operation. Greatly extended periods of uninterrupted operation of 'diesel engines are thus possible with these improved oils.

Since, as noted above, silver metal containing bearings are more and more common in diesel engines, the corrosive effect of the lubricating an compositions of the invention on silver bearings is determined in comparisonwith a conventional oxidation and corrosion inhibited compounded lubricating oil. This test is run in a 4-cylinder diesel engine using one percent sulfur fuel. The procedure is the same as outlined in the Navy propulsion load tests given above. The conventional oxidation and corrosion inhibited compounded oil is a solvent refined SAE 40 viscosity mineral lubricating oil having a viscosity index of 60. It contains 10 mM./kg. of zinc dialkyl dithiophosphate and 0.25 percent by weight of a sulfurized diparafiin sulfide. The uninhibited reference oil previously described and shown to be highly corrosive to copper-lead bearings, is also evaluated. In- Iustrative test results are given in the following table:

From the above test data it will be seen that the conventional oxidation and corrosion inhibited compounded lubricating oil causes a much greater silver bearing weight loss than the lubricating oil compositions of the invention. Although the weight losses of both the reference oil and the compositions of the invention are low, it must be borne in mind that the reference oil has been shown to be unsatisfactory in the copper-lead bearing tests set out above. It is a further fact, aside from corrosion losses, that silvermetahcontaining bearings are extremely sensitive to lubricant compositions containing active sulfur type corrosion inhibitors and such compositions generally provide an unsatisfactorily low degree of lubricity for silver bearing surfaces.

The antioxidant properties of the lubricating oil compositions of the invention are also evaluated in tests for determining the oxidation inhibition period. In these tests the oil is contained in 'a large glass tube equipped with a high speed .glass stirrer. The oil temperature is 340 F. and a pressure of about one atmosphere of pure oxygen is maintained. The volume of oxygen added is automatically recorded and the time in hours required for- 100 grams of oil to absorb 1200 cubic centimeters of oxygen is called the inhibition period. The reference oilis a highly refined turbine oil, a straight mineral lubrieating oil, of the acid refined white oil type. Illustrative test results are as follows:

Table VI Inhibition Oll Period in Hours Highly refined turbine oil (ref. oi1),. 0. 0 0.5% di(2 'ethylhexane'diol-l,3)arsenitein reference oil 0. 0 1 Q hYZ QS B d -L3). t nit i r c 0H..- 0.0 0.5% di(2 ethylhexanediol-1,3) arsenate in reference oil. 0.0 1.0% mono (pentaerythritol'nionooleate) arsenite inref e1 ce 0 ,0 0.' 0.2% phenyl-alpha-naphthylain fr 3. a 0.2% 4-tert.-butylcatechol in reference oil 2. 9 0.2% phenyl-al ha-naphthylamiue and 0.5% di(2rethylhexanediol-Liii arsenite in reference oil 56. 0 0.2% phenyl-alpha-naphthylamine and 0.5% mono(2- ethylhexanediol-lfi) arsenite in reference oil 40+ 0.2% phenyl-aIpha-naphthylamjne and 0.5% di(2-"ethylheXanediol-L3) arsenatein reference oil 40+ 0.2% phenyl-alpha-naphthy1amine and 1.0% mono(pent erythritol monooleate) arsenite in reference oil- 40+ 0.2% 4-tert.-buty1catechol and 0.5% di(2-ethylhexanediol- 1,3) arsenite in reference oil 7. 4 0.2% 4-tert.-butyleatechol and 0.5% mono(2-ethylhexanedun-1,3) arsenite in referenceoil. 7. 9 0.2% 4-tert.-butylcatechol and 0.5% di(2-ethylhexanedlol- 1,3) arsenate in reference oil 6. 3 0.2% 4-te'rt.-butylcatechol and 1.0% mono(pentaerythritol monooleate) arsenite in reference oi 6. 9

The test data of the above tables showthat lubricating oil compositions containing the complexes of the invention may be effectively inhibited against oxidation whereas similar lubricating o il compositions without the acid complexes are susceptible to a very high rate of oxidation. The test results of the above tables also show that when conventional oxidation inhibitors of the diaryl amine and polyhydroxy benzene ytype illustrated by pheny -anaphthylamine and 4-'t-butylcatechol, respectively, are employed in thdcoinpositions according to this invention, a marked improvement in-the effect of the primary oxidation inhibitor is obtainedindicating synergism of the conventional antioxidant and the complex. This improvement is particularly noticeable when the preferred diaryl amine type of primary oxidation inhibitor is employed in combination with the complex. 7

Other conventional oxidation inhibitors of the diaryl amine type which are suitable for employment in the improved compositions of the invention include p-hydro'xy diphenyl amine, p,-p-dihydroxy diphenyl amine, diphenylp-phenylene diarnine, diphenyl amine, phenothiazine, dibet-a-naphthylamine, etc. Other polyhydroxy aromatic compoundsinclude l,2 dihydroxy naphthalene, hydroquinone, di'- t butyl resorcinol, 1,2 dihydroxy- 4- amino naphthalene,'etc. Other oxidation inhibitors of these general types are also'we-ll known in the art.

In the compositions of the invention including both conventional oxidation inhibitors and the complexes, any amount of the conventional "inhibitor sufficient to inhibit oxidation and any amount of the complex sufficient to enhance the action of the conventional inhibitor may be employed. Ordinarily, amounts of from 0.1 to 5.0 percent by weight of the composition of the conventional inhibitor and the complex each are sufficient. Preferably from 0.05 to 2 percent by weight of each inhibitor is employed in operations where there is little danger of encountering extremely high temperatures. The amounts of conventional inhibitor and complex need not be the same in any given composition.

The nature of the improved lubricating oil compositions of the invention and their effectiveness should be readily apparent from the many illustrations given above. Oxidation and corrosivity in the compositidhs due to oxidative deterioration are definitely inhibited to a very substantial degree. Particularly corrodible rrietals such as engine alloy bearings of copper, lead, and the like, as well as bearings of silver, are not adversely affected. This is indeed remarkable since the problem of devising lubricant compositions uniformly noncorrosive to both types of bearing metals has long confronted workers in the art. As shown by the actual tests set out above, the advantages of these improvements are obtained without hydroxy benzene.

11 loss of other desirable properties of the lubricant compositions.

As mentioned above, the arsenic and antimony compounds of the compositions according to this invention are preferably formed from an arsenic or antimony acid or salts thereof and an alphaor beta-diol or vicinal di- Although the present invention is in no way limited to any theory concerning the structure of the compounds, it is believed that they may be illustrated by the following formulae:

RaC-O C-0 0 J iOH R2-O/ J iOH Rr-O-O GO Monoglycol arsenates or antimonntes H: R: &O 011 (ii-0 OH I H+ R2o 11+ CO OHJ CO OH 24! 2 Monoglycol arsenltes or antimonites OH R: OH R: R:C-O O-CR2 l-0 O-( J X R2C X CRz RzC-O O-C-R2 C-0 OC Dlglycol arsenates or antimonates R: R R] B: (1-0 OJ; v-o (HE i I to RC i CR2 11+ O OC O0 OO 1'1, l. l. in

Diglycol arsenites or antlmonltes 0 a on R ii on R i 11+ \0/ \OH Monopyrocatechol Monopyrocatechol arsenntes 0r antimonates arsenites or antimonltes O OH 0 I R Dlpyrocateohol arsenates or antimonates R X R H+ 0 o .1

Dipyrocatechol arsenites or antimonltes Trlpyrocatechol arsenates or antlmonates Trlglycol arsenates or anttmonates wherein X is arsenic or antimony and R is hydrogen or a group of hydrocarbon structure as previously described.

Although the above types of compounds are distinctly preferred in the compositions of the invention, other compounds of similar structure having substituents on the hydrocarbon groups which do not adversely afiect the reaction may likewise be employed. Such substituents include: hydroxyl groups, as when a polyhydroxy alcohol or benzene such as glycerol, pentaerythritol, sorbitol or trihydroxy benzene is used; ester groups, as when glycerol monooleate or sorbitan monooleate is used; and halogens, ethers, amides, etc., as will be apparent to those skilled in the art from the above description of the invention.

Although the compositions of the invention have been primarily described as crankcase lubricants for internal combustion engines, they are also useful as turbine oil s, hydraulic fluids, instrument oils, constituent oils in grease manufacture, ice-machine oils, and the like.

We claim:

1. A lubricant composition comprising an oil of lubricating viscosity and a member of the group consisting of arsenites, arsenates, antimonites, and antimonates of alphaand beta-glycols of 6 to 10 carbon atoms and 4-tert.-butyl pyrocatechol in an amount sufiicient to inhibit corrosion.

2. A lubricant composition comprising an oil of lubricating viscosity and 0.01 to 5.0 percent by weight based on the oil of an arsenite of 2-ethylhexane-1,3-diol.

3. A lubricant composition comprising an oil of lubricating viscosity and from about 0.01 to about 5.0 percent by weight based on the oil of an arsenite of 4-tert.-butyl pyrocatechol.

4. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and a member of the group consisting of arsenites, arsenates, antimonites, and antimonates of alphaand beta-glycols of 6 to 10 carbon atoms and 4-tert.-butyl pyrocatechol in an amount sufiicient to inhibit corrosion.

5. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and an arsenate of an alpha-alkanediol containing from 6 to 10 carbon atoms in an amount suflicient to inhibit corrosion.

6. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and an arsenate of a beta-alkanediol containing from 6 to 10 carbon atoms in an amount suflicient to inhibit corrosion.

7. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and an arsenite of an alpha-alkanediol containing from 6 to 10 carbon atoms in an amount suflicient to inhibit corrosion.

8. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and an arsenite of a beta-alkanediol containing from 6 to 10 carbon atoms in an amount sufiicient to inhibit corrosion.

9. A lubricant composition comprising a mineral 1ubricating oil for internal combustion engines which is nor- 13 mally corrosive to alloy bearings and from about 0.01 to about 5.0 percent by weight based on the oil of an arsenate of 2-ethy1hexane-1,3-diol.

10. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and from about 0.01 to about 5 .0 percent by weight based on the oil of an arsenate of: 4-tert.-buty1 pyrocatechol.

11. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings, from about 0.01 to about 5.0 percent by weight based on the oil of a member of the group consisting of arsenites, arsenates, antimonites, and antimonates of alphaand beta-glycols of 6 to 10 carbon atoms and 4-tert.-butyl pyrocatechol and from about 0.01 to about 5.0 percent by weight based on the oil of a diaryl amine oxidation inhibitor.

12. A lubricant composition comprising a mineral lu- References Cited in the file of this patent UNITED STATES PATENTS 2,144,654 Guthmann ct a1 Jan. 24, 1939 2,161,184 McKone et a1 June 6, 1939 2,305,627 Lincoln et a1. Dec. 22, 1942 2,410,652 Griflin et a1. Nov. 5, 1946 2,465,296 Swiss Mar. 22, 1949 

1. A LUBRICANT COMPOSITION COMPRISING OF AN OIL OF LUBRICATING VISCOSITY AND A MEMBER OF THE GROUP CONSISTING OF ARSENITES, ARSENATES, ANTIMONITES, AND ANTIMONATES OF ALPHA- AND BETA-GLYCOLS OF 6 TO 10 CARBON ATOMS AND 4-TERT.-BUTYL PYROCATECHOL IN AN AMOUNT SUFFICIENT TO INHIBIT CORROSION. 